Genetic Integrity of the Mitochondrial Genome

Eukaryotic cells contain two independent but interactive genetic systems com-prising of nuclear DNA and mitochondrial DNA (mtDNA). MtDNA represents less than 1% of total cellular DNA. However, it encodes gene products essential for cellular function. Thus, damage to mtDNA either by endogenous or environmental agents can impair cellular functions.1 Unlike nuclear DNA, human mtDNA contains no introns, has no protective histones, and is exposed to reactive oxygen species (ROS) generated by oxidative phosphorylation. Replication of mtDNA could also be prone to error.2–5 Perhaps due to these reasons, mtDNA accumulates mutations at least 10 times more frequently than does nuclear DNA.6,7